Labor, the Greens and crossbench MPs have accused Mr Turnbull of using the delay to avoid an embarrassing backbench revolt over a banking Commission of Inquiry or a move to reverse Sunday penalty rate cuts.

Asked about the reports, Ms Bishop said: "I can't begin to speculate what this is about."

"Nobody has raised that with me," she said.

Ms Bishop also defended the decision to delay parliament for a week, saying it was necessary to deal with an outstanding citizenship issues.

Meanwhile, Mr Turnbull has told reporters in Sydney this morning the decision was "just common sense".

It would give the government the time needed to deal with same-sex marriage legislation and any citizenship issues, which he said were the "two major issues" Parliament needed to address before the end of the year.

The delay gives the lower house two extra weeks after the same-sex marriage bill passes the senate.